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==What is the cardiac frequency?==
{{nav|
[[Image:ECGpapier.png|thumb| De breedte van een hokje op het ECG geeft de tijd weer]]
|previouspage=Rhythm
[[Image:Ecgfreq.png|thumb| De aftelmethode om de hartfrequentie te bepalen. Het tweede QRS-complex ligt tussen de ''75'' en de ''60'' slagen per minuut. Deze hartslag ligt daar dus tussenin, rond de 65 slagen per minuut. ]]
|previousname=Step 1: Rhythm
Een vrij eenvoudige vraag en met wat rekenwerk makkelijk te beantwoorden.
|nextpage=Conduction
|nextname=Step 3:Conduction intervals (PQ, QRS, QT, QTc)
}}
[[Image:ECGpapier.png|thumb|300px| The width of a square on the ECG represents time]]
[[Image:Ecgfreq.png|thumb|300px| The count method to determine the heart frequency. The second QRS complex is between ''75'' and ''60'' beat per minute. This heartbeat is between that, around 65 beats per minute.]]
'''What is the heart rate?'''
To answer this question, determine the time between two QRS complexes. Previously, the ECG was printed on a paper strip transported through an ECG writer at the speed of 25 mm/second. Now, digital ECGs are common; however, the method for determining the frequency remains the same. The ECG has a grid with thick lines 5 mm apart (= 0,20 second) and thin lines 1 mm (0,04 second).  


Het ECG papier liep destijds met 25 mm/seconde door het ECG apparaat. Tegenwoordig worden ECG's digitaal geregistreerd, maar het principe is hetzelfde. Het ECG papier heeft een raster verdeling. Grote hokjes zijn 5 mm breed = 0,20 seconde. Kleine hokjes zijn 1 mm breed = 0,04 seconde.
There are three simple methods to determine the heart rate (HR)


'''Er zijn drie eenvoudige manieren om de hartfrequentie (HF) te berekenen:'''
{| class="wikitable"
# De kleine (1mm) hokjes tellen tussen twee QRS-complexen. Omdat de standaardsnelheid van het papier 25 mm/sec is:&nbsp;&nbsp;&nbsp;[[Afbeelding:HFformule.png]]<br>  Deze methode is vooral handig bij het meten van een snelle hartslag (>100 slagen/min)
!The square counting method
# De aftel methode (het liefst te gebruiken bij een normale sinusritme). Hierbij gebruikt men de sequentie 300-150-100-75-60-50-43-37. Men begint met aftellen bij een willekeurig QRS-complex. Dit is het startpunt. De daarop volgende grote hokje is 300, de volgende 150 enz. Men stopt met tellen bij het volgende QRS-complex. Valt deze tussen twee aftelpunten dan neemt men een gemiddelde.
|-
# De 3 seconde marker methode (te gebruiken bij onregelmatige ritmen). Tel het aantal QRS-complexen die binnnen een tijdsbestek van 3 seconden vallen (tussen twee markers die sommige ECG apparaten aangeven). Deze vermenigvuldigt men dan met 20. Dit levert het aantal slagen per minuut.
| The '''square counting''' method is ideal for regular heart rates. Use the sequence 300-150-100-75-60-50-43-37. Count from the first QRS complex, the first thick line is 300, the next thick line 150 etc. Stop the sequence at the next QRS complex. When the second QRS complex is between two lines, take the mean of the two numbers from the sequence or use the fine-tuning method listed below.
|}


{| class="wikitable"
!Use a calculator
|-
| Count the small (1mm) squares between two QRS complexes. The ECG paper runs at 25 mm/sec through the ECG printer; therefore:[[Image:HFformule_en.png|none]]This method works well in case of tachycardia (>100 beats/minute)<br>
|}


'''Finetuning van de aftelmethode'''
{| class="wikitable"
Met de volgende kleinere onderverdelingen kan bovengenoemde aftelmethode nog nauwkeuriger gebruikt worden:
!The marker method
*'''300'''''-250-214-187-167-'''''150'''
|-
*'''150'''''-136-125-115-107-'''''100'''
|
*'''100'''''-94-88-83-79-'''''75'''
Non-regular rhythms are best determined with the "3 second marker method". Count the number of QRS complexes that fit into 3 seconds (some ECG writers print this period on the ECG paper). Multiply this number by 20 to find the number of beats/minute.
*'''75'''''-71-68-65-62-'''''60'''
|}


{| class="wikitable" font-size="90%" align="center"
|+'''The 'square counting' method can be fine-tuned with the following sequence'''
|-
|'''300'''||250||214||187||167||'''150'''||136||125||115||107||'''100'''||94||88||83||79||'''75'''||71||68||65||62||'''60'''
|-
|}
{{clr}}
{{clr}}


==Wat beïnvloedt de hartfrequentie?==
==What changes the frequency of the heart?==
De hartfrequentie wordt door een groot aantal factoren bepaald.
A number of factors change the heart frequency, including:
* Het autonome zenuwstelsel, de sympathicus en parasympathicus.  
* the (para) sympathic nervous system.  
** Het '''sympathisch systeem''' o.i.v. epinephrine (=adrenaline) leidt bij activatie tot een toename in atrioventriculaire geleiding, prikkelbaarheid en contractiliteit. (in de oertijd goed voor: ''fight, fright, flight'')
** The '''sympathic system''', e.g. epinephrine, (=adrenalin) increases atrioventricular conduction and contractility (the ''fight or flight'' reaction.)
** Het parasympathische systeem (nervus vagus) o.i.v. acetycholine leidt daarentegen bij activatie  tot een afname in frequentie van de SA-knoop, atrioventriculaore voortgeleiding en prikklebaarheid. In tegenstelling tot het sympathisch systeem werkt het parasympathicus voornamelijk op de atria.
** The parasympathic system (nervus vagus,) e.g. acetycholine, decreases the frequency and atrioventricular conduction. The parasympathic system affects mainly the atria.
* De vulling van het hart. Bij ondervulling gaat de frequentie omhoog
* Cardiac filling increases the frequency.
*  [[arrhythmias]] influence heart rate.
 
[[Category:ECG Course]]

Latest revision as of 19:51, 15 March 2011

«Step 1: Rhythm Step 3:Conduction intervals (PQ, QRS, QT, QTc)»


The width of a square on the ECG represents time
The count method to determine the heart frequency. The second QRS complex is between 75 and 60 beat per minute. This heartbeat is between that, around 65 beats per minute.

What is the heart rate? To answer this question, determine the time between two QRS complexes. Previously, the ECG was printed on a paper strip transported through an ECG writer at the speed of 25 mm/second. Now, digital ECGs are common; however, the method for determining the frequency remains the same. The ECG has a grid with thick lines 5 mm apart (= 0,20 second) and thin lines 1 mm (0,04 second).

There are three simple methods to determine the heart rate (HR)

The square counting method
The square counting method is ideal for regular heart rates. Use the sequence 300-150-100-75-60-50-43-37. Count from the first QRS complex, the first thick line is 300, the next thick line 150 etc. Stop the sequence at the next QRS complex. When the second QRS complex is between two lines, take the mean of the two numbers from the sequence or use the fine-tuning method listed below.
Use a calculator
Count the small (1mm) squares between two QRS complexes. The ECG paper runs at 25 mm/sec through the ECG printer; therefore:
HFformule en.png
This method works well in case of tachycardia (>100 beats/minute)
The marker method

Non-regular rhythms are best determined with the "3 second marker method". Count the number of QRS complexes that fit into 3 seconds (some ECG writers print this period on the ECG paper). Multiply this number by 20 to find the number of beats/minute.

The 'square counting' method can be fine-tuned with the following sequence
300 250 214 187 167 150 136 125 115 107 100 94 88 83 79 75 71 68 65 62 60


What changes the frequency of the heart?

A number of factors change the heart frequency, including:

  • the (para) sympathic nervous system.
    • The sympathic system, e.g. epinephrine, (=adrenalin) increases atrioventricular conduction and contractility (the fight or flight reaction.)
    • The parasympathic system (nervus vagus,) e.g. acetycholine, decreases the frequency and atrioventricular conduction. The parasympathic system affects mainly the atria.
  • Cardiac filling increases the frequency.
  • arrhythmias influence heart rate.
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